Rework the warning suppression macros

[derobins]

The macros in H5warnings.h have several flaws:

• The compiler name(s) appear in the macros, which means that we sometimes either have multiple macro lines around problematic code or we wind up with "combo" macros like the gcc-clang macros that will be awkward to extend to new compilers.
• The macros are simple replacements for individual pragma lines, so any ifdef complications have to be handled in the library code, not H5warnings.h. These ifdefs and the comments that explain them will have to be duplicated throughout the library code.
• The name of the suppressed warning may not be very informative. For example, passing MPI_STATUSES_IGNORE as a parameter to MPI calls can raise spurious stringop-overflow warnings w/ gcc. It'd be nice to have a warning suppression that clearly indicated the nature of the (non-)problem.

We should replace the existing scheme with one that uses a wider set of macros that hide ifdef complexity and can be more easily extended to other compilers (e.g., MSVC).

Example:

/* Disable warnings concerning non-standard extensions, like F16 */
/* clang */
#if defined(__clang__)
#define H5_WARN_NONSTD_SUFFIX_OFF H5_WARN_OFF("pedantic")
#define H5_WARN_NONSTD_SUFFIX_ON  H5_WARN_ON("pedantic")
/* gcc 14+ */
#elif defined(__GNUC__) && __GNUC__ >= 14
#define H5_WARN_NONSTD_SUFFIX_OFF H5_WARN_OFF("c11-c23-compat")
#define H5_WARN_NONSTD_SUFFIX_ON  H5_WARN_ON("c11-c23-compat")
/* gcc 9-13 */
#elif defined(__GNUC__) && __GNUC__ >= 9
#define H5_WARN_NONSTD_SUFFIX_OFF H5_WARN_OFF("c11-c2x-compat")
#define H5_WARN_NONSTD_SUFFIX_ON  H5_WARN_ON("c11-c2x-compat")
#else
/* Everything else */
#define H5_WARN_NONSTD_SUFFIX_OFF
#define H5_WARN_NONSTD_SUFFIX_ON
#endif

[jhendersonHDF]

Agreed. The c11-c2x-compat / c11-c23-compat flag is an annoyance due to the changed and deprecated name between versions.

[qkoziol]

Agree - something like this will be more scalable

[byrnHDF]

Can't we use a general name and create that actual details in the compiler-specific files.

[derobins]

Can't we use a general name and create that actual details in the compiler-specific files.

I've thought about how to do that, but it would be awkward and probably awful to maintain. Different warnings will have different ifdef soup and the macro names are inside the ifdefs. I'd much rather maintain a dozen macros with a similar layout than a complicated, error-prone cut-n-paste macro scheme.

[derobins]

I have this work essentially completed. I'll try to get a PR in this week.